A method of displaying the inner cavity of a hollow organ such as a blood vessel, a large bowel or the like in a virtual endoscope display style by using an image scanned by using a medical image diagnosis device such as an X-ray CT device, an MRI device or the like is useful to observe the shape of the inner wall of the hollow organ. Particularly, in a large bowel region, it is possible to observe the inner wall of the large bowel without inserting an endoscope into a body. Therefore, this method is a less invasive and much attention is paid to this method as an examination method imposing little mental and physical burden on an examinee.
In addition to a virtual endoscope image created by the method described above, an MPR (Multi Planner Reconstruction) image, etc. are also known as an image used when a large bowel is examined by using the medical image diagnosing apparatus, and a panoramic image has been proposed as a characteristic display image (patent document 1). The panoramic image is an image which is displayed like a specimen as if a hollow organ is cut open in a long axis direction, and this has been expected as a method of reducing a burden of interpretation of radiogram because this method makes it possible to command a panoramic view of the inner wall of the hollow organ. Particularly when the inner wall of a large bowel is observed, the panoramic image makes it possible to observe the inner wall of the large bowel on plane, and thus makes it easy to detect polyp or the like existing between folds of the large bowel which may be overlooked in the virtual endoscope image.
The panoramic image can be created by radiating a virtual light beam in a radial direction from each point on the center line of the inner cavity of a large bowel region, projecting a pixel value or reflection light at an impinging portion of the virtual light beam against the inner wall of the large bowel onto the inner surface of one linear hollow cylindrical model, cutting open the cylindrical model in the long axis direction thereof and unrolling the inner surface of the cylindrical model onto a plane.